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Capillary rise or fall in a tube. Jurin's law , or capillary rise , is the simplest analysis of capillary action —the induced motion of liquids in small channels [ 1 ] —and states that the maximum height of a liquid in a capillary tube is inversely proportional to the tube's diameter .
Capillary action of water (polar) compared to mercury (non-polar), in each case with respect to a polar surface such as glass (≡Si–OH). Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of external forces like gravity.
When a capillary tube is inserted into a liquid, the liquid will rise or fall in the tube, due to an imbalance in pressure. The characteristic height is the distance from the bottom of the meniscus to the base, and exists when the Laplace pressure and the pressure due to gravity are balanced.
An interesting phenomena, capillary rise of water (as pictured to the right) provides a good example of how these properties come together to drive flow through a capillary tube and how these properties are measured in a system. There are two general equations that describe the force up and force down relationship of two fluids in equilibrium.
Illustration of capillary rise and fall. Red=contact angle less than 90°; blue=contact angle greater than 90° If a tube is sufficiently narrow and the liquid adhesion to its walls is sufficiently strong, surface tension can draw liquid up the tube in a phenomenon known as capillary action.
Any transient rise in plasma colloid osmotic pressure or fall in capillary hydrostatic pressure sufficient to allow reverse (negative) causes unopposed diffusion of interstitial proteins to the subglycocalyx space, reducing the colloid osmotic pressure difference that was driving absorption of fluid to the capillary.
The equation is derived for capillary flow in a cylindrical tube in the absence of a gravitational field, but is sufficiently accurate in many cases when the capillary force is still significantly greater than the gravitational force. In his paper from 1921 Washburn applies Poiseuille's Law for fluid motion in a circular tube.
The interfacial (surface) tension, St, (dyne cm −1), can be calculated by applying the equation of capillary rise method (when the contact angle Ө → 0): = where: h (cm) is the height of Hg column above the Hg meniscus in the capillary; r (cm) is the radius of capillary